PHENOL COMPOUNDS AS NEW MATERIALS FOR ELECTRON SPIN RESONANCE DOSIMETRY IN RADIOTHERAPY

Abstract

Introduction: Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the electron spin resonance (ESR) arouses increasing interest for applications in various therapy procedures. Free radicals are known to be produced when a compound is irradiated with ionizing radiations. The concentration of radiationinduced free radicals is proportional to the absorbed dose and this allows for dosimetric measurements through ESR technique which enables to quantitatively determine the radical concentration. In this work we report the ESR investigation of phenol pellets and thin films exposed to various types of radiation beams (clinical photon and electron beams, mix field neutrons/photons). Phenols are compounds possessing a benzene ring attached to a OH group. After irradiation the final product is a stable phenoxy radical. Materials and methods: Thanks to their size, the phenolic films here presented are good devices for the dosimetry of beams with high dose gradient and which require accurate knowledge of the precise dose delivered. Photon and electron irradiations at various energies were performed with the Siemens Primus Lowlinear accelerator present at ARNAS Ospedale Civico di Palermo, Italy. Thermal neutron irradiations were performed at the thermal neutron column at the Triga Mark II reactor of LENA (Laboratorio Energia Nucleare Applicata) of Pavia, Italy. ESR dosimeters were readout by means of a Bruker ECS106 spectrometer equipped with a TE102 rectangular cavity at room temperature. Results: The dose response of both pellets and films was found to be linear for all beams used in the dose range analyzed. The signal is very stable in the first days after irradiation. The possibility of obtaining depth dose profile was investigated. Conclusions: In conclusion, the phenols show radiometric features that designate it as a new material for EPR.